Non-gelled curable compositions containing imide functional compositions

ABSTRACT

The present invention is directed to a non-gelled, curable composition including at least one compound having a plurality of imide functional groups. The compound in particular contains a reaction product of at least one secondary monoamine and at least one maleimide, and is suitable for use in coatings and castings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a division of U.S. patent application Ser.No. 11/005,374, filed Dec. 6, 2004, and entitled: “NON-GELLED CURABLECOMPOSITIONS CONTAINING IMIDE FUNCTIONAL COMPOUNDS”, and is related toU.S. patent application Ser. No. 11/005,375, filed Dec. 6, 2004, andentitled: NON-GELLED CURABLE COMPOSITIONS CONTAINING IMIDE FUNCTIONALCOMPOUNDS”.

FIELD OF THE INVENTION

The present invention relates to imide functional compounds used innon-gelled, curable compositions, suitable for use as coatings andcastings.

BACKGROUND OF THE INVENTION

In microelectronic circuit packages, circuits and units are prepared inpackaging levels of increasing scale. Generally, the smallest scalepackaging levels are semiconductor chips housing multiple microcircuitsand/or other components. Such chips are usually made from ceramics,silicon, and the like. Intermediate package levels (i.e., “chipcarriers”) comprising multi-layer substrates may have attached thereto aplurality of small-scale chips housing many microelectronic circuits.Likewise, these intermediate package levels themselves can be attachedto larger scale circuit cards, motherboards, and the like. Theintermediate package levels serve several purposes in the overallcircuit assembly including structural support, transitional integrationof the smaller scale microcircuits and circuits to larger scale boards,and the dissipation of heat from the circuit assembly. Substrates usedin conventional intermediate package levels have included a variety ofmaterials, for example, ceramic, fiberglass reinforced polyepoxides, andpolyimides.

Dielectric materials used as coatings on the substrates must meetseveral requirements, including conformality, flame resistance, andcompatible thermal expansion properties. Conventional dielectricmaterials include, for example, polyimides, polyepoxides, phenolics, andfluorocarbons. A common method of applying conformal coatings is byvapor deposition. Electrophoretic deposition has also been explored;however, polyimide resins such as bismaleimide resins, while desired fortheir superior dielectric and thermal stability properties, areintractable in most solvents, let alone aqueous dispersions, makingelectrophoretic deposition of such resins virtually impossible.Reactivity of the resins with amines increases the difficulty offormulation in both solvent based and aqueous dispersed coatings.

Accordingly, it would be desirable to provide a composition thatprovides the dielectric and thermal stability properties necessary forelectronic circuit applications, while allowing for convenientelectrophoretic deposition thereof.

SUMMARY OF THE INVENTION

The present invention is directed to a non-gelled, curable compositioncomprising at least one compound having a plurality of imide functionalgroups. The compound comprises at least one tertiary amino functionalsuccinimide.

DETAILED DESCRIPTION OF THE INVENTION

Other than in any operating examples, or where otherwise indicated, allnumbers expressing quantities of ingredients, reaction conditions and soforth used in the specification and claims are to be understood as beingmodified in all instances by the term “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical values, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

By “polymer” is meant a polymer including homopolymers and copolymers,and oligomers. Unless stated otherwise, molecular weights are numberaverage molecular weights for polymeric materials indicated as “M_(n)”and obtained by gel permeation chromatography using a polystyrenestandard in an art-recognized manner. By “composite material” is meant acombination of two or more differing materials.

The compositions of the present invention are curable compositions. Asused herein, the terms “curable” and “substantially cured” as used inconnection with a curable composition means that any crosslinkablecomponents of the composition are at least partially crosslinked after acuring process (e. g., heating). In certain embodiments of the presentinvention, the crosslink density (degree of crosslinking) of thecrosslinkable components ranges from 5% to 100% of completecrosslinking. One skilled in the art will understand that the presenceand degree of crosslinking, i.e., the crosslink density, can bedetermined by a variety of methods, such as dynamic mechanical thermalanalysis (DMTA) using a Polymer Laboratories MK III DMTA analyzerconducted under nitrogen. This method determines the glass transitiontemperature and crosslink density of free films of coatings or polymers.These physical properties of a cured material are related to thestructure of the crosslinked network.

The compositions of the present invention are additionally non-gelled.By “non-gelled” is meant that prior to a curing process, the compositionis substantially free from crosslinking, and the composition has ameasurable intrinsic viscosity when dissolved in a suitable solvent, asdetermined, for example, in accordance with ASTM-D1795 or ASTM-D4243. Incontrast, a gelled composition, having an essentially infinite molecularweight, would have an intrinsic viscosity too high to measure.

The compositions of the present invention are suitable for use asmolding compounds, film-forming compositions (e. g., coatingcompositions), fiberglass sizing, and the like. They are often used asfilm-forming compositions. In particular, the compositions of thepresent invention are suitable for use as coatings in electronicapplications, such as for chip scale packages, printed circuit boards,and the like, due to their superior dielectric and thermal stabilityproperties.

The compositions of the present invention comprise at least one compoundhaving a plurality of cyclic imide functional groups. The compoundcomprises in particular at least one tertiary amino functionalsuccinimide. Typically the tertiary amino functional succinimidecomprises a reaction product of at least one secondary monoamine and atleast one maleimide.

The secondary monoamine used to prepare the tertiary amino functionalsuccinimide may be aliphatic or aromatic. In an embodiment of thepresent invention, the secondary monoamine comprises an aliphaticsecondary monoamine. Nonlimiting examples of secondary monoamine includediethylamine, methylethyl amine, dibutylamine, and mixtures thereof. Thesecondary monoamine may include non-reactive heteroatoms such as O andS, and/or ring structures. A non-limiting example includesbis-2-methoxyethylamine. Secondary alkanolamines such as methylethanolamine, diethanolamine, and the like are also suitable. The amount ofsecondary monoamine used to prepare the tertiary amino functionalcompound is usually about 40 to 100 percent by equivalent, often 70 to100 percent by equivalent, based on the total equivalents of maleimideused to prepare the compound.

The maleimide used to prepare the tertiary amino functional compound ofthe present invention may include any N-substituted maleimide, such asN-phenylmaleimide. The maleimide may be derived from aniline and/oraniline-formaldehyde condensation polymers. In certain embodiments themaleimide comprises a bismaleimide, which may be derived from, forexample, 1,1′-(methylenedi-4,1-phenylene)bismaleimide such as BMI-1000,polyphenylmethane maleimide, such as BMI-2000, m-phenylenebismaleimide,such as BMI-3000, bisphenol A diphenyl ether bismaleimide, such asBMI-4000, and 3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylmethanebismaleimide, all available from Miki Sangyo (USA), Inc.

In certain non-limiting embodiments of the present invention, thetertiary amino functional compound comprises a reaction product of atleast one secondary monoamine, at least one maleimide and at least oneprimary amine. The secondary monoamine and maleimide may be as describedabove. The primary amine may be any compound containing at least oneprimary amine group, including polyamines. The primary amine typicallycomprises at least one lower alkyl amine having from 1 to 10 carbonatoms. Often the primary amine is selected from methyl amine,butylamine, ethylamine, dimethylaminopropylamine and mixtures thereof.

The amount of primary amine should be chosen to avoid gelation of thereaction mixture. When primary amines are used, the total amount ofamine (primary and secondary) should be greater than 75 percent byequivalent, based on the total equivalents of maleimide used to preparethe compound. The primary amine may be used in amounts ranging from 5 to99 percent by equivalent, provided that enough secondary amine ispresent to provide greater than 75 percent total amine, based on thetotal equivalents of maleimide.

The curable composition of the present invention may also becharacterized as comprising at least one compound having the followingstructure:

wherein m is greater than or equal to one, usually greater than or equalto two; R¹ and R² may be the same or different and each is independentlyselected from lower alkyl groups having from one to twelve carbon atomsand aryl groups having from six to twenty carbon atoms; and Q is amonovalent or polyvalent organic radical derived from a saturated,unsaturated, or aromatic hydrocarbon. R¹ and R² may be independentlylinear, branched, or cyclic, and may be substituted, provided thesubstituents do not interfere with the preparation of the compound. In aparticular embodiment both R¹ and R² are butyl groups. Q is often apolyvalent organic aromatic radical.

The tertiary amino functional succinimide compound used in thecomposition of the present invention is typically water-dispersible. By“water-dispersible” is meant able to be solubilized, dispersed oremulsified in water.

The tertiary amino functional succinimide described above can be presentin the composition of the present invention in amounts up to 100 percentby weight. When the composition includes other resinous components asdescribed below, the tertiary amino functional succinimide is usuallypresent at a level of 3 to 40 percent by weight, or 5 to 20 percent byweight, based on the total weight of resin solids of the composition.

In certain non-limiting embodiments of the present invention, thecomposition further comprises at least one crosslinkable film-formingpolymer. The polymer may contain ionic groups in particular embodiments;for example, when the film-forming composition is electrodepositable.The polymer may contain functional groups in particular embodiments.Such functional groups can include, for example, epoxy groups, vinylgroups, blocked isocyanate groups, ester groups, activehydrogen-containing groups such as thiol, hydroxyl, carboxylic acid,carbamate, amine, phenolic hydroxyl, and combinations thereof. Inaddition, both ionic groups and functional groups may be present on thefilm-forming polymer.

When the film-forming composition comprises at least one crosslinkablefilm-forming polymer, the composition may further comprise at least onecuring agent capable of reacting with appropriate functional groups onthe polymer.

The polymer used in the composition of the present invention typicallyis a water-dispersible, film-forming polymer. The water-dispersiblepolymer may be ionic in nature; that is, the polymer can contain anionicfunctional groups to impart a negative charge or cationic functionalgroups to impart a positive charge. Most often, the polymer containscationic salt groups, for example cationic amine salt groups.

Non-limiting examples of film-forming resins suitable for use as thepolymer in the composition of the present invention, in particular inanionic coating compositions, include base-solubilized, carboxylic acidgroup-containing polymers such as the reaction product or adduct of adrying oil or semi-drying fatty acid ester with a dicarboxylic acid oranhydride; and the reaction product of a fatty acid ester, unsaturatedacid or anhydride and any additional unsaturated modifying materialswhich are further reacted with polyol. Also suitable are the at leastpartially neutralized interpolymers of hydroxy-alkyl esters ofunsaturated carboxylic acids, unsaturated carboxylic acid and at leastone other ethylenically unsaturated monomer. Still another suitableresin comprises an alkyd-aminoplast vehicle, i.e., a vehicle containingan alkyd resin and an amine-aldehyde resin. Another suitable anionicresin composition comprises mixed esters of a resinous polyol. Thesecompositions are described in detail in U.S. Pat. No. 3,749,657 at col.9, lines 1 to 75 and col. 10, lines 1 to 13. Other acid functionalpolymers also can be used such as phosphatized polyepoxide orphosphatized acrylic polymers as are well known to those skilled in theart. Additionally, suitable for use as the polymer are those resinscomprising one or more pendent carbamate functional groups, for example,those described in U.S. Pat. No. 6,165,338.

In particular embodiments of the present invention, the polymercomprises a cationic, active hydrogen-containing electrodepositableresin capable of deposition on a cathode. Non-limiting examples of suchcationic film-forming resins include amine salt group-containing resinssuch as the acid-solubilized reaction products of polyepoxides andprimary or secondary amines such as those described in U.S. Pat. Nos.3,663,389; 3,984,299; 3,947,338; and 3,947,339. Usually, these aminesalt group-containing resins are used in combination with a blockedisocyanate curing agent as described in detail below. The isocyanate canbe fully blocked as described in the aforementioned U.S. Pat. No.3,984,299 or the isocyanate can be partially blocked and reacted withthe resin backbone such as described in U.S. Pat. No. 3,947,338. Also,one-component compositions as described in U.S. Pat. No. 4,134,866 andDE-OS No. 2,707,405 can be used in the composition of the presentinvention as the polymer. Besides the epoxy-amine reaction productsdiscussed immediately above, the polymer can also be selected fromcationic acrylic resins such as those described in U.S. Pat. Nos.3,455,806 and 3,928,157.

Besides amine salt group-containing resins, quaternary ammonium saltgroup-containing resins also can be employed. Examples of these resinsinclude those which are formed from reacting an organic polyepoxide witha tertiary amine salt. Such resins are described in U.S. Pat. Nos.3,962,165; 3,975,346; and 4,001,101. Examples of other cationic resinsare ternary sulfonium salt group-containing resins and quaternaryphosphonium salt-group containing resins such as those described in U.S.Pat. Nos. 3,793,278 and 3,984,922, respectively. Further, cationiccompositions prepared from Mannich bases such as described in U.S. Pat.No. 4,134,932 can be used.

In one embodiment of the present invention, the polymer can comprise oneor more positively charged resins which contain primary and/or secondaryand/or tertiary amine groups. Such resins are described in U.S. Pat.Nos. 3,663,389; 3,947,339; and 4,116,900. In U.S. Pat. No. 3,947,339, apolyketimine derivative of a polyamine such as diethylenetriamine ortriethylenetetraamine is reacted with a polyepoxide. When the reactionproduct is neutralized with acid and dispersed in water, free primaryamine groups are generated. Also, equivalent products are formed when apolyepoxide is reacted with excess polyamines such as diethylenetriamineand triethylenetetraamine and the excess polyamine vacuum stripped fromthe reaction mixture. Such products are described in U.S. Pat. Nos.3,663,389 and 4,116,900.

In certain non-limiting embodiments of the present invention, thepolyepoxide may be derived from a polyglycidyl ether of a polyphenol,chain-extended with a halogenated 4,4′-isopropylidenediphenol. Suitableexamples include tetrachloro-4,4′-isopropylidenediphenol(tetrachlorobisphenol A) and tetrabromo-4,4′-isopropylidenediphenol(tetrabromobisphenol A), as disclosed in U.S. Pat. No. 6,713,587. Suchpolymers may improve flame retardance of the composition, which isparticularly advantageous in electronic applications. These polymers maybe rendered cationic in a manner similar to those described above forother polyepoxides.

Mixtures of the above-described ionic resins also can be usedadvantageously. In one embodiment of the present invention, the polymerhas cationic salt groups and may be at least one of a polyepoxide-basedpolymer having primary, secondary and/or tertiary amine groups (such asthose described above) and an acrylic polymer having hydroxyl and/oramine functional groups.

As previously discussed, in one particular embodiment of the presentinvention, the polymer has cationic salt groups. In this instance, suchcationic salt groups typically are formed by solubilizing the resin withan inorganic or organic acid such as those conventionally used inelectrodepositable compositions. Suitable examples of solubilizing acidsinclude, but are not limited to, sulfamic, acetic, lactic,alkanesulfonic such as methanesulfonic, and formic acids. Sulfamic andlactic acids are most commonly employed.

The polymer described above can be present in the composition of thepresent invention in amounts ranging from 30 to 97 percent by weight,usually 40 to 95 percent by weight, based on the total weight of resinsolids in the composition.

As mentioned above, the composition of the present invention may furthercomprise a curing agent reactive with the active hydrogens of thepolymer described immediately above. Note that the terms “curing agent”and “crosslinking agent” are used interchangeably. Blocked organicpolyisocyanate, betahydroxy urethane and aminoplast curing agents aresuitable for use in the present invention, although blocked isocyanatestypically are employed for cathodic electrodeposition.

Aminoplast resins are the condensation products of amines or amides withaldehydes. Examples of suitable amine or amides are melamine,benzoguanamine, urea, carbamates, acrylamide polymers, and similarcompounds. Generally, the aldehyde employed is formaldehyde, althoughproducts can be made from other aldehydes such as acetaldehyde andfurfural. The condensation products contain methylol groups or similaralkylol groups depending on the particular aldehyde employed. Mostoften, these methylol groups are etherified by reaction with an alcohol.Various alcohols employed include monohydric alcohols containing from 1to 4 carbon atoms such as methanol, ethanol, isobutyl alcohol, andn-butanol, with methanol being used most often. Aminoplast resins arecommercially available from American Cyanamid Co. under the trademarkCYMEL and from Monsanto Chemical Co. under the trademark RESIMENE.

The aminoplast curing agents, when present, typically are utilized inconjunction with an active hydrogen-containing anionic polymer and arepresent in amounts ranging from about 5 to 50 percent by weight, oftenfrom 5 to 25 percent by weight, the percentages based on the totalweight of the resin solids in the composition.

The curing agents commonly employed in cathodic electrodepositioncompositions are blocked polyisocyanates. The polyisocyanates can befully blocked as described in U.S. Pat. No. 3,984,299 column 1 lines 1to 68, column 2 and column 3 lines 1 to 15, or partially blocked andreacted with the polymer backbone as described in U.S. Pat. No.3,947,338 column 2 lines 65 to 68, column 3 and column 4 lines 1 to 30,which are incorporated by reference herein. By “blocked” is meant thatthe isocyanate groups have been reacted with a compound such that theresultant blocked isocyanate group is stable to active hydrogens atambient temperature but reactive with active hydrogens in the filmforming polymer at elevated temperatures usually between 90° C and 200°C.

Suitable polyisocyanates include aromatic and aliphatic polyisocyanates,including cycloaliphatic polyisocyanates and representative examplesinclude diphenylmethane-4,4′-diisocyanate (MDI), 2,4- or 2,6-toluenediisocyanate (TDI), including mixtures thereof, p-phenylenediisocyanate, tetramethylene and hexamethylene diisocyanates,dicyclohexylmethane-4,4′-diisocyanate, isophorone diisocyanate, mixturesof phenylmethane-4,4′-diisocyanate and polymethylenepolyphenylisocyanate. Higher polyisocyanates such as triisocyanates canbe used. An example would includetriphenylmethane-4,4′,4″-triisocyanate. Isocyanate prepolymers withpolyols such as neopentyl glycol and trimethylolpropane and withpolymeric polyols such as polycaprolactone diols and triols (NCO/OHequivalent ratio greater than 1) can also be used.

The polyisocyanate curing agents typically are utilized in conjunctionwith the active hydrogen-containing cationic electrodepositable polymerin amounts ranging from ranging from 5 to 55 percent by weight, usually5 to 40 percent by weight, based on the total weight of resin solids inthe composition.

Also suitable are beta-hydroxy urethane curing agents such as thosedescribed in U.S. Pat. Nos. 4,435,559 and 5,250,164. Such beta-hydroxyurethanes are formed from an isocyanate compound, for example, any ofthose described immediately above, a 1,2-polyol and/or a conventionalblocking such as monoalcohol. Also suitable are the secondary amineblocked aliphatic and cycloaliphatic isocyanates described in U.S. Pat.Nos. 4,495,229 and 5,188,716.

The composition of the present invention may further contain a varietyof additives including coalescing solvents, pigments, thixotropes,plasticizers, extenders, stabilizers, and antioxidants, as are commonlyused in the art.

In an embodiment of the present invention, when the composition is usedas a dielectric coating on a circuit substrate, the composition canfurther comprise a rheology modifier as mentioned above, which canassist in the deposition of a smooth and uniform thickness of thedielectric coating on the surface of the substrate, including on thesurface of hole or via walls as well as the edges, including the edgesat the via openings (without obstructing the holes), on a circuitsubstrate. Any of a variety of the rheology modifiers well-known in thecoatings art can be employed for this purpose.

One suitable rheology modifier comprises a cationic microgel dispersionprepared by dispersing in aqueous medium a mixture of a cationicpolyepoxide-amine reaction product which contains amine groups,typically primary amine groups, secondary amine groups and mixturesthereof, and a polyepoxide crosslinking agent, and heating the mixtureto a temperature sufficient to crosslink the mixture, thus forming acationic microgel dispersion. Such cationic microgel dispersions andtheir preparation are described in detail in U.S. Pat. No. 5,096,556 atcolumn 1, line 66 to column 5, line 13, incorporated by referenceherein. Other suitable rheology modifiers include the cationic microgeldispersion having a shell-core morphology described in detail in EP 0272 500 B1. This microgel is prepared by emulsification in aqueousmedium of a cationic film-forming resin and a thermosetting crosslinkingagent, and heating the resultant emulsion to a temperature sufficient tocrosslink the two components.

The cationic microgel is present in the composition of the presentinvention in an amount sufficient to effect adequate rheology controland hole edge coverage, but insufficient to adversely affect flow of thecomposition upon application or surface roughness of the cured coating.For example, the cationic microgels described immediately above can bepresent in the resinous phase of the composition in an amount rangingfrom 0.1 to 30 weight percent, typically from 1 to 20 weight percentbased on the weight of total resin solids present in the resinous phase.

When the composition described above is electrophoretically depositedand cured to form a cured film (as described in detail below), the curedfilm can have a dielectric constant of no more than 3.50, often no morethan 3.30, or no more than 3.00, or no more than 2.80. Also, the curedfilm typically has a dielectric loss factor of less than or equal to0.02, or less than or equal to 0.015, or less than or equal to 0.01.

A dielectric material is a non-conducting substance or insulator. The“dielectric constant” is an index or measure of the ability of adielectric material to store an electric charge. The dielectric constantis directly proportional to the capacitance of a material, which meansthat the capacitance is reduced if the dielectric constant of a materialis reduced. A low dielectric material is desired for high frequency,high speed digital where the capacitances of substrates and coatings arecritical to the reliable functioning of circuits. For example, presentcomputer operations are limited by coupling capacitance between circuitpaths and integrated circuits on multi-layer assemblies since computingspeed between integrated circuits is reduced by this capacitance and thepower required to operate is increased. See Thompson, Larry F., et al.,Polymers for Microelectronics, presented at the 203^(rd) NationalMeeting of American Chemical Society, Apr. 5-10, 1992.

The “dielectric loss factor” is the power dissipated by a dielectricmaterial as the friction of its molecules opposes the molecular motionproduced by an alternating electric field. See I. Gilleo, Ken, Handbookof Flexible Circuits, at p. 242, Van Nostrand Reinhold, New York (1991).See also, James J. Licari and Laura A. Hughes, Handbook of PolymerCoatings for Electronics, pp. 114-18, 2^(nd) ed., Noyes Publication(1990) for a detailed discussion of dielectric materials and dielectricconstant.

The dielectric constant of the cured composition can be measured by anyof the methods used in the art. For purposes of the present invention,one suitable method uses electrochemical impedance spectroscopy asfollows.

The coating sample is prepared by application of the composition to asteel substrate and subsequent curing to provide a cured dielectriccoating having a film thickness of 0.85 mil (20.83 microns). A 32 squarecentimeter free film of the cured dielectric coating is placed in theelectrochemical cell with 150 milliliters of electrolyte solution (1 MNaCl) and allowed to equilibrate for one hour. An AC potential of 100 mVis applied to the sample and the impedance is measured from 1.5megahertz to 1 hertz frequency range. The method employs aplatinum-on-niobium expanded mesh counter electrode and a singlejunction silver/silver chloride reference electrode. The dielectricconstant of the cured coating is determined by calculating thecapacitance at 1 megahertz, 1 kilohertz, and 63 hertz, and solving thefollowing equation for E.C=E ₀ EA/dwhere C is the measured capacitance at discrete frequency (in Farads);E₀ is the permitivity of free space (8.854187817¹²); A is the samplearea (32 square centimeters); d is the coating thickness; and E is thedielectric constant. It should be noted the values for dielectricconstant as used in the specification and in the claims is thedielectric constant determined as described above at a frequency of 1megahertz. Values for the dielectric loss factor as used in thespecification and in the claims represent the difference between thedielectric constant measured at a frequency of 1 megahertz as describedabove, and the dielectric constant for the same material measured at afrequency of 1.1 megahertz.

Any of the previously described electrodepositable cationic compositionscan be electrophoretically applied to an electroconductive core of amulti-layer circuit assembly. The applied voltage for electrodepositionmay be varied and can be, for example, as low as 1 volt to as high asseveral thousand volts, but typically between 50 and 500 volts. Thecurrent density is usually between 0.5 ampere and 5 amperes per squarefoot (0.5 to 5 milliamperes per square centimeter) and tends to decreaseduring electrodeposition indicating the formation of an insulatingconformal film on all exposed surfaces of the core. As used herein andin the specification and in the claims, by “conformal” film or coatingis meant a film or coating having a substantially uniform thicknesswhich conforms to the substrate topography, including the surfaceswithin (but not occluding) any holes that may be present. After thecoating has been applied by electrodeposition, it is cured, e. g.,thermally cured, at elevated temperatures ranging from 90° to 300° C.for a period of 1 to 40 minutes, to form a conformal dielectric coatingover all exposed surfaces of the core.

The dielectric coating is of uniform thickness and often is no more than50 microns, usually no more than 25 microns, and typically no more than20 microns. A lower film thickness may be desirable for a variety ofreasons. For example, a dielectric coating having a low film thicknessallows for smaller scale circuitry. Also, a coating having a lowdielectric constant (as discussed above) may allow for a dielectriccoating having a lower film thickness and also can minimize capacitivecoupling between adjacent signal traces.

Those skilled in the art would recognize that prior to theelectrophoretic application of the dielectric coating, the core surfacemay be pretreated or otherwise prepared for the application of thedielectric. For example, cleaning, rinsing, and/or treatment with anadhesion promoter prior to application of the dielectric may beappropriate.

Moreover, it should be understood, that any of the aforementionedcompositions can be applied by a variety of application techniques wellknown in the art other than electrodeposition, for example, byroll-coating, immersion, or spray application techniques. In suchinstances, it may be desirable to prepare the composition at higherresin solids content. Also, for such applications, the polymer may ormay not include solubilizing or neutralizing acids to form cationic saltgroups.

Suitable substrates to be used as the core are any electricallyconductive materials. For example, suitable metals include copper foil,iron-nickel alloys, and combinations thereof. A preferred iron-nickelalloy is Invar, (trademark owned by Imphy S. A., 168 Rue de Rivoli,Paris, France) comprising approximately 64 weight percent iron and 36weight percent nickel. This alloy has a low coefficient of thermalexpansion, comparable to that of silicon materials used to preparechips. This property is desirable in order to prevent failure ofadhesive joints between successively larger or smaller scale layers of achip scale package, due to thermal cycling during normal use. When anickel-iron alloy is used as the electrically conductive core, a layerof copper metal is preferably applied to all surfaces of theelectrically conductive core to ensure optimum conductivity. The layerof copper metal may be applied by conventional means, such aselectroplating or metal vapor deposition. The layer of copper typicallyhas a thickness of from 1 to 8 microns.

In a particular embodiment, suitable substrates include perforateelectrically conductive cores having a thickness of about 15 to 250microns, preferably 25 to 100 microns. By “perforate electricallyconductive core” is meant an electrically conductive mesh sheet having aplurality of holes spaced at regular intervals. Typically the holes areof uniform size and shape. When the holes are circular, which istypical, the diameter of the holes is about 8 mil (203.2 microns). Theholes may be larger or smaller as necessary, with the proviso that ahole is large enough to accommodate all the layers applied withoutbecoming obstructed. The spacing of the holes is about 20 mils (508microns) center-to-center, but again may be larger or smaller asnecessary. Via density may range from 500 to 10,000 holes/square inch(75 to 1550 holes/square centimeter), preferably about 2500 holes/squareinch (387.5 holes/square centimeter).

The film-forming composition of the present invention, serving as adielectric coating, may be applied to all exposed surfaces of theelectrically conductive core to form a conformal coating. As a conformalcoating, the dielectric is of substantially uniform thickness, typicallyabout 5 to 50 microns on all exposed surfaces of the metal core. Afterapplication of the dielectric coating, holes or vias may be formed inthe surface of the dielectric coating in a predetermined pattern toexpose sections of the core. Such holes may be formed by laser ablation,mechanical drilling and chemical or plasma etching techniques.

Metallization can be performed after the via-forming step by applying alayer of metal to all surfaces, allowing for the formation of metallizedvias in the core. Suitable metals include copper or any metal or alloywith sufficient conductive properties. The metal can be applied, forexample, by electroplating or any other suitable method known in the artto provide a uniform metal layer. The thickness of this metal layer canrange from 1 to 50 microns, typically from 5 to 25 microns.

To enhance the adhesion of the metal layer to the dielectric coating,prior to the metallization step all surfaces can be treated with ionbeam, electron beam, corona discharge or plasma bombardment followed byapplication of an adhesion promoter layer to all surfaces. The adhesionpromoter layer can range from 50 to 5000 Ångstroms thick and istypically a metal or metal oxide selected from chromium, titanium,nickel, cobalt, cesium, iron, aluminum, copper, gold, tungsten, andzinc, and alloys and oxides thereof.

After metallization, a resinous photosensitive layer (i.e. “photoresist”or “resist”) is applied to the metal layer. Optionally, prior toapplication of the photoresist, the metallized substrate can be cleanedand/or pretreated; e.g., treated with an acid etchant to remove oxidizedmetal. The resinous photosensitive layer can be a positive or negativephotoresist. The photoresist layer can have a thickness ranging from 1to 50 microns, typically 5 to 25 microns, and can be applied by anymethod known to those skilled in the photolithographic processing art.Additive or subtractive processing methods may be used to create thedesired circuit patterns.

Suitable positive-acting photosensitive resins include any of thoseknown to practitioners skilled in the art. Examples includedinitrobenzyl functional polymers such as those disclosed in U.S. Pat.No. 5,600,035, columns 3-15. Such resins have a high degree ofphotosensitivity. In one embodiment, the resinous photosensitive layeris a composition comprising a dinitrobenzyl functional polymer,typically applied by spraying.

The resinous photosensitive layer may comprise an electrodepositablecomposition comprising a dinitrobenzyl functional polyurethane and anepoxy-amine polymer such as that described in Examples 3-6 of U.S. Pat.No. 5,600,035.

Negative-acting photoresists include liquid or dry-film typecompositions. Any of the previously described liquid compositions may beapplied by spray, roll-coating, spin coating, curtain coating, screencoating, immersion coating, or electrodeposition application techniques.Preferably, liquid photoresists are applied by electrodeposition, morepreferably cationic electrodeposition. Electrodepositable photoresistcompositions comprise an ionic, polymeric material which may be cationicor anionic, and may be selected from polyesters, polyurethanes,acrylics, and polyepoxides. Examples of photoresists applied by anionicelectrodeposition are shown in U.S. Pat. No. 3,738,835. Photoresistsapplied by cationic electrodeposition are described in U.S. Pat. No.4,592,816. Examples of dry-film photoresists include those disclosed inU.S. Pat. Nos. 3,469,982, 4,378,264, and 4,343,885. Dry-filmphotoresists are typically laminated onto the surface such as byapplication of hot rollers.

Note that after application of the photosensitive layer, the multi-layersubstrate may be packaged at this point allowing for transport andprocessing of any subsequent steps at a remote location.

Alternatively, after the photosensitive layer is applied, a photo-maskhaving a desired pattern may be placed over the photosensitive layer andthe layered substrate exposed to a sufficient level of a suitableradiation source, typically an actinic radiation source. As used herein,the term “sufficient level of radiation” refers to that level ofradiation which polymerizes the monomers in the radiation-exposed areasin the case of negative acting resists, or which depolymerizes thepolymer or renders the polymer more soluble in the case of positiveacting resists. This results in a solubility differential between theradiation-exposed and radiation-shielded areas.

The photo-mask may be removed after exposure to the radiation source andthe layered substrate developed using conventional developing solutionsto remove more soluble portions of the photosensitive layer, and uncoverselected areas of the underlying metal layer. The metal uncovered maythen be etched using metal etchants which convert the metal to watersoluble metal complexes. The soluble complexes may be removed by waterspraying.

The photosensitive layer protects the underlying substrate during theetching step. The remaining photosensitive layer, which is impervious tothe etchants, may then be removed by a chemical stripping process toprovide a circuit pattern connected by the metallized vias.

After preparation of the circuit pattern on the multi-layered substrate,other circuit components may be attached to form a circuit assembly.Additional components include, for example, one or more smaller scalecomponents such as semiconductor chips, interposer layers, larger scalecircuit cards or mother boards and active or passive components. Notethat interposers used in the preparation of the circuit assembly may beprepared using appropriate steps of the process of the presentinvention. Components may be attached using conventional adhesives,surface mount techniques, wire bonding or flip chip techniques. High viadensity in the multi-layer circuit assembly prepared in accordance withthe present invention allows for more electrical interconnects fromhighly functional chips to the packages in the assembly.

The following examples are intended to illustrate various embodiments ofthe invention, and should not be construed as limiting the invention inany way. Examples 1-3 demonstrate the preparation of succinimides inaccordance with the present invention. Example 4 illustrates thepreparation of a polyisocyanate curing agent. Example 5 demonstrates thepreparation of an amine functional polyepoxide resin, and Examples 6 and7 explain the preparation of electrodepositable resins. Curablefilm-forming compositions are illustrated in Examples A to C. Unlessotherwise indicated, all parts are by weight (grams).

EXAMPLE 1

This example describes the preparation of an alkylamino functionalsuccinimide for use in a coating composition. The succinimide wasprepared as described below from the following ingredients: Parts byweight (in Ingredients grams) BMI 2000¹ 150.0 Dibutylamine 104.7Methylisobutyl ketone 180.0¹Polyphenylmethane maleimide, available from Miki Sangyo (USA), Inc.,Parsippany, NJ.

The above ingredients were mixed in order in a 1-liter flask at roomtemperature and allowed to exotherm. The mixture exothermed to 37° C.,then was heated to 50° C. After 55 minutes stirring at 50° C., thereaction was a homogeneous brown liquid measuring 57.9% solids, whichsolidified upon sitting overnight at room temperature.

EXAMPLE 2

This example describes the preparation of a mixed alkylamino functionalsuccinimide for use in a coating composition. The succinimide wasprepared as described below from the following ingredients: Parts byweight (in Ingredients grams) BMI 2000 150.0 Diethylamine 29.6Dibutylamine 52.3 Methylisobutyl ketone 210.0

The above ingredients were placed, in order, in a 500 ml flask undernitrogen and stirred without added heat. The reaction exotherm peaked at46° C. after 40 minutes. The mixture was held at 55° C. for 30 minutes,then cooled to give a brown solution at 51.6% solids.

EXAMPLE 3

This example describes the preparation of an alkylamino functionalsuccinimide for use in a coating composition, in which approximately 10%of the maleimide groups remain unreacted. The succinimide was preparedas described below from the following ingredients: Parts by weight (inIngredients grams) BMI 2000 150.0 Methylisobutyl ketone 180.0Dibutylamine 94.2

The BMI 2000 and methylisobutyl ketone were stirred in a 1-liter flaskunder nitrogen and stirred without heat. The dibutylamine was added over50 minutes. Upon completion of the addition, the reaction had reached49° C. The mixture was heated to 55° C. and held at that temperature for45 minutes. The reaction was cooled giving a brown solution at 55.8%solids which solidified after standing overnight at room temperature.

EXAMPLE 4

This example describes the preparation of a blocked polyisocyanatecuring agent. The blocked polyisocyanate was prepared as described belowfrom the following ingredients: Parts by weight (in Ingredients grams)DESMODUR ® N3300¹ 4268.0 Methylisobutyl ketone 918.0 Methylethylketoxime 1875.7 Methylisobutyl ketone 166.2¹Polyfunctional hexamethylene diisocyanate available from Bayer Corp.

The DESMODUR N3300 and first amount of methylisobutyl ketone were heatedto 48° C. in a 12-liter flask under nitrogen. The methylethyl ketoximewas added over 3 hours, maintaining a reaction temperature of less then90° C. during the addition. The second amount of methylisobutyl ketonewas added as a rinse, and the reaction was held at 90° C. until theisocyanate functionality was gone as determined by IR spectroscopy. Thecrosslinker was 85% solids.

EXAMPLE 5

This example describes the preparation of an amine functionalpolyepoxide resin. The polyepoxide was prepared as described below fromthe following ingredients: Parts by weight (in Ingredients grams)MAZON ® 1651¹ 225.0 EPON ® 828² 1133.0 Tetrabromobisphenol A 1042.3TETRONIC ® 150R1³ 0.3 Aminopropyl 172.1 diethanolamine Diethanolamine74.4 Ethylene glycol 946.5 monobutyl ether EPON 828 48.4¹A flexibilizer, commercially available from BASF Corporation.²Diglycidyl ether of bisphenol A having an epoxy equivalent weight of188, available from Resolution Performance Products.³A surfactant, available from BASF Corporation.

The MAZON 1651, EPON 828, Tetrabromobisphenol A and TETRONIC 15OR1 wereplaced in a 5-liter flask. The mixture was heated to 70° C., and held atthat temperature for 15 minutes. The aminopropyl diethanolamine anddiethanolamine were added and a rapid exotherm observed, peaking at 179°C. The mixture was allowed to slowly cool while stirring for one hour.The ethylene glycol monobutyl ether was added over 1.5 hours starting ata temperature of 141° C. The second charge of EPON 828 was added and thereaction held for one hour at 125° C. The reaction was cooled to give asolution at 75% solids.

EXAMPLE 6

This example describes the preparation of a cationic amine saltfunctional polyepoxide resin with an alkylamino functional succinimidemixed with the polymer. The electrodepositable resin was prepared asdescribed below from the following ingredients: Parts by weight (inIngredients grams) Amine functional resin 1500.0 of Example 5Succinimide of Example 1 215.9 Sulfamic acid 76.2 Deionized water 152.3Deionized water 1844.7 Deionized water 200.0

The amine functional resin of Example 5 and the succinimide of Example 1were placed in a 5-liter flask. The mixture was heated to 62° C, thenthe sulfamic acid and first amount of deionized water were added,whereupon the temperature dropped to 55° C. The heat was removed, andthe second amount of water was added over 2.5 hours. Due to highviscosity, the third amount of water was added to give a viscousdispersion at 32.2% solids.

EXAMPLE 7

This example describes the preparation of a cationic amine saltfunctional polyepoxide resin. The resin has a mixture of both alkylaminofunctional succinimide and blocked polyisocyanate. Theelectrodepositable resin was prepared as described below from thefollowing ingredients: Parts by weight (in Ingredients grams) Ethyleneglycol 93.7 monohexyl ether EPON 828 377.7 Tetrabromo bisphenol A 347.5TETRONIC 150R1 0.12 Diethanolamine 24.8 Aminopropyldiethanolamine 57.4Methylisobutyl ketone 107.0 Methylisobutyl ketone 50.0 Blockedpolyisocyanate 346.5 of Example 4 Succinimide of Example 3 165.0

The ethylene glycol monohexyl ether, EPON 828, tetrabromo bisphenol A,and TETRONIC 150R1 were placed in a 3-liter flask under nitrogen andheated to 70° C. After holding at this temperature for 15 minutes, theheat was turned off and the diethanolamine and aminopropyldiethanolaminewere added. The reaction exotherm peaked after 11 minutes at 146° C.,and cooled slowly over 30 minutes. At 124° C., then first amount ofmethylisobutyl ketone was added over 22 minutes and the reaction washeld at 125° C. until two hours after the peak exotherm. The secondportion of methylisobutyl ketone was added over 13 minutes while coolingto 100° C. When the reaction reached 100° C., the blocked polyisocyanateof Example 4 and the succinimide of Example 3 were added. The resin(1334.2 g) was added to a 43° C. solution of 21.0 g sulfamic acid, 0.82g lactic acid (88% in water) and 528.1 g deionized water under vigorousagitation using a high lift blade. To this dispersion was added 10.4 ggum rosin (30% solution in MAZON 1651) and the dispersion was mixed for30 minutes. An additional 733.1 g deionized water was added over 48minutes. An additional 600 g deionized water was added due to highviscosity, in two equal portions. A further 500 g deionized water wasadded, and the dispersion was distilled under vacuum, removing 877.4 gdistillate. 377.4 g Deionized water was added to give a milky dispersionat 39.81 % solids.

COATING EXAMPLES Example A

Parts by weight (in Ingredients grams) Electrodepositable resin ofExample 6 582.3 Ethyleneglycol monohexyl ether 18.7 Deionized water1899.0

The electrodepositable resin of Example 6 was weighed into a beaker anddeionized water was slowly added while hand stirring with a stainlesssteel spatula. Water additions and stirring continued until theviscosity of the mixture was such as to be easily stirred. The ethyleneglycol monohexyl ether was then added to the mixture and hand stirredwith a stainless steel spatula to form a thick consistent mixture. Theremaining deionized water was then slowly added to the mixture whileunder agitation.

A 4″×12″ aluminum panel from Q-Panel Lab Products was coated with thisbath from a glass beaker. A stainless steel heating/cooling coil servedas the counter electrode (anode) for coat outs. The bath was agitatedusing a magnetic stirrer and the temperature of the bath was held at105° F. The panel was immersed in the bath and a coat out voltage of 35volts was applied for 2 minutes. These conditions produced a film buildof approximately 19 microns following a bake of 217° C. for 30 minutesin an electric oven. Following bake, the coated film showed no effectfollowing 100 double acetone rubs.

Example B

Parts by weight (in Ingredients grams) Electrodepositable resin ofExample 8 470.9 Ethyleneglycol monohexyl ether 18.7 Deionized water2010.4

The electrodepositable resin of Example 8 was mixed in a 1 gallonplastic container with enough deionized water to enable stirring thebath with an electric mixer equipped with a flat paddle blade. Theethylene glycol monohexyl ether was added to the bath under agitation.This mixture was allowed to stir for approximately 20 minutes, at whichtime the remaining deionized water was added. The paint bath was thenultrafiltered 50% by volume, the ultrafiltrate being replaced bydeionized water. The coating bath was transferred to a glass beaker anda 4″×12″ aluminum panel from Q-Panel Lab Products was coated in a set upsimilar to that used in Formulation Example 1. The panel was immersed inthe coating bath, maintained at 105° F., and a coat out voltage of 100volts was applied for 2 minutes. These conditions resulted in films witha thickness of approximately 21 microns following a bake of 225° C. for30 minutes in an electric oven. These films were unaffected following100 double acetone rubs.

Example C

The succinimide of Example 2 was applied to a 4″×12″ aluminum panel fromQ-Panel Lab Products using a #42 wirewound drawdown bar. The coating wasbaked for 30 minutes at 225° C. in an electric oven, resulting in a filmwith a thickness of approximately 23 microns. This film was unaffectedfollowing 100 double acetone rubs.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the scope of the inventionas defined in the appended claims.

1. A non-gelled, curable composition comprising at least one compoundhaving a plurality of cyclic imide functional groups, wherein thecompound comprises a reaction product of at least one secondarymonoamine and at least one maleimide, wherein the non-gelled, curablecomposition comprises a film-forming composition, and wherein thefilm-forming composition further comprises at least one crosslinkablefilm-forming polymer.
 2. The composition of claim 1 wherein thefilm-forming polymer contains ionic salt groups.
 3. The composition ofclaim 1 wherein the film-forming polymer contains activehydrogen-containing groups.
 4. The composition of claim 3, wherein thefilm-forming composition further comprises at least one curing agenthaving functional groups that are reactive with the activehydrogen-containing groups of the film-forming polymer.
 5. Thecomposition of claim 4, wherein the curing agent is selected frombeta-hydroxy urethane, blocked organic polyisocyanate and aminoplastcuring agents, and mixtures thereof.
 6. The composition of claim 1,wherein the film-forming polymer comprises amine functional groups. 7.The composition of claim 6, wherein the film-forming polymer comprisescationic salt groups.
 8. The composition of claim 2, wherein thecomposition comprises an electrodepositable composition.
 9. Anon-gelled, curable composition comprising at least one compound havingthe following structure:

wherein m is greater than or equal to one; R¹ and R² may be the same ordifferent and each is independently selected from lower alkyl groupshaving from one to twelve carbon atoms and aryl groups having from sixto twelve carbon atoms; and Q is a monovalent or polyvalent organicradical derived from a saturated or unsaturated, aliphatic or aromatichydrocarbon, and wherein the film-forming composition further comprisesat least one film-forming polymer.
 10. The composition of claim 9wherein the film-forming polymer contains ionic salt groups.
 11. Thecomposition of claim 9 wherein the film-forming polymer contains activehydrogen-containing groups.
 12. The composition of claim 11, wherein thefilm-forming composition further comprises at least one curing agenthaving functional groups that are reactive with the activehydrogen-containing groups of the film-forming polymer.
 13. Thecomposition of claim 12, wherein the curing agent is selected frombeta-hydroxy urethane, blocked organic polyisocyanate and aminoplastcuring agents, and mixtures thereof.
 14. The composition of claim 9,wherein the film-forming polymer comprises amine functional groups. 15.The composition of claim 10, wherein the polymer comprises cationic saltgroups.
 16. The composition of claim 10, wherein the compositioncomprises an electrodepositable composition.